The present invention relates to a method and a device for a digital modulation.
A modulator is used for the modulation of a useful signal onto a carrier signal. A modulator is frequently used in transmission systems, like, for example, in wire-bonded or wireless communication systems.
In different communication systems, here different types of modulation are used for the modulation of information included in the useful signal onto the carrier signal. Examples for this are modulation types which use a phase modulation and/or an amplitude modulation.
In particular in a mobile communication system, like, e.g., a mobile radio system having a time-limited energy supply, it is here desirable for the modulator to comprise a high power efficiency. Thus, a low energy consumption and thus a longer operation time of a corresponding terminal device may be achieved.
In particular in the field of mobile radio, a parallel propagation of different communication standards exists, like, e.g., of GSM, EDGE, UMTS, HSUPA, WLAN, Wimax, DECT, Bluetooth, etc. The same use different modulation types. In some standards the same are present in a combined way to achieve higher bandwidths. It is accordingly possible to provide modulators which may execute a modulation for different communication standards. For example, high-frequency transmission devices exist which may execute both a GMSK modulation with a constant envelope of the output signal for a GSM mobile radio system and an 8-PSK modulation with a non-constant envelope for an EDGE mobile radio system.
Current solutions utilize a Cartesian modulator architecture or a polar modulator architecture. They have the disadvantage, however, that they comprise a high portion of analog circuit blocks. These disadvantages, compared to digital circuit blocks, are, for example, a greater error and/or distortions by analog filter adaptations in the representation of constellation points of the modulation scheme used. Such deviations are, for example, indicated with the so-called error vector magnitude (EVM). By a direct current portion (DC offset) in signal processing, an increased loss of the carrier signal results (carrier leakage). All in all, a higher power consumption thus results which is not wanted particularly in mobile terminal devices.
When using analog circuit blocks, compared to digital circuit blocks a greater chip area is needed if the transmission device is arranged in an integrated member. In this connection, additional problems result with the scaling of circuit structures when using new, minimized semiconductor technologies.
It is thus desirable for a transmission device to comprise a highest possible portion of digital circuit blocks or a high portion of switched logical blocks, respectively.
The present invention is based on the problem of providing a method for a power-efficient modulation and/or a power-efficient modulation device.
This object is achieved by the method having the features of patent claim 1 and/or by the modulation device having the features of patent claim 5.
The method for modulating a signal alternating between a first polarity and a second polarity onto a carrier signal comprises the following steps:                providing an inverted carrier signal,        determining a polarity of the signal,        mixing the signal with the carrier signal when the signal comprises the first polarity, and        mixing the signal with the inverted carrier signal when the signal comprises the second polarity.        
The modulation device for modulating a signal alternating between a first polarity and a second polarity onto a carrier signal comprises an inverter for providing an inverted carrier signal. Further, it comprises a means for determining a polarity of the signal. Further, it comprises a mixer cell which is coupled to the inverter and to the means and which is implemented such that it mixes the signal with the carrier signal when the signal comprises the first polarity and that it mixes the signal with the inverted carrier signal when the signal comprises the second polarity.
Different advantageous implementations and embodiments of the invention result from the dependent claims.